This invention relates to a membrane filtration apparatus for effecting filtration of a liquid composition wherein a feed liquid is introduced into the apparatus and a filtrate stream is removed from the apparatus. More particularly, this invention relates to a tangential flow membrane filtration apparatus or dead ended membrane filtration apparatus which are formed and selectively sealed by injection molding of a polymeric composition.
Prior to the present invention, liquids have been filtered within a plurality of filter modules that are stacked between manifolds or individually sealed to a manifold plate. Each module includes a one or more filter layers separated by appropriate spacer layers, such as screens, to permit liquid feed flow into the apparatus as well as filtrate flow from the apparatus. Filtration within the module can be conducted as a tangential flow process wherein incoming feed liquid is flowed tangentially over a membrane surface to form a retentate and a filtrate. Alternatively, filtration can be conducted as a dead end mode wherein all incoming feed liquid is passed through a membrane filter with retention of solids and other debris on the membrane filter. In this latter mode only a filtrate is recovered.
At the present time, filtrate is sealed from feed within a membrane filtration apparatus by sealing techniques utilizing potting adhesives, solvent bonding or heat sealing. In the case of a tangential flow filtration apparatus, filtrate is sealed from feed and retentate. Adhesives are undesirable since they have limited chemical compatibility, are a source of significant extractable species, introduce process control difficulties, impose bond strength limitations, impose use temperature limitations and increase process cycle time. Heat sealing is undesirable since its use imposes a limitation upon the thickness of the material being heat sealed. In addition, heat sealing is undesirable because it requires multiple steps, imposes material compatibility limitations and requires a substrate to effect heat sealing of filtration elements. Solvent bonding is undesirable since solvents impose environmental limitations and impose limitations on liquids to be filtered.
Accordingly, it would be desirable to provide a multilayer filtration apparatus which utilizes a plurality of filtration modules wherein the layers are appropriately sealed without the use of adhesive, solvent bonding or heat sealing. In addition, it would be desirable to provide a tangential flow or a dead ended filtration apparatus containing a plurality of filtration modules which can be formed into a stack and which can be appropriately sealed to define liquid flow paths within the stack in a one step sealing process.